In a number of different technical fields a need has arisen for systems that are capable of automatically "reading" strings of alphanumeric characters. One example is a system for recognising and recording car number plates as part of a vehicle monitoring and control system. Another application, and one of increasing commercial importance, is in container code verification in a container port.
Cargo containers are each provided with a unique identification code which must be checked and verified every time a container is moved into or out of a container port. The codes are applied to the containers normally by stencil or by some other means on the side of the container. Conventionally such codes are read by an operator and entered manually into the computer system controlling operations in the cargo terminal. This is clearly inefficient and an automated system for reading the codes and entering the data directly into the control system would be desirable.
Automating this process has numerous problems, however. To begin with, there is no fixed size for the characters and no standard typeface. The precise location of the code may vary from container to container. The container may be dirty, there may be good or poor contrast between the characters and the background. The system must be capable of identifying characters in natural light and artificial light, good weather and bad. To be effective to replace current manual systems any automated system must have a very high degree of accuracy and reliability in all these conditions.